Apparatus for cutting of fiber strands

ABSTRACT

An apparatus for chopping strands of fibers in which there is provided a rotatable clamping head defined by two disc-shaped members, means for forcing the members against each other and chopping knives clamped between the disc members and protruding therefrom, each knife being defined by a straight metal body of substantially triangular cross-section having a first portion clamped between the disc-shaped members and a second portion protruding beyond the disc-shaped members, with the protruding portion having a knife edge.

ijnited States Patent 11 1 Eichler et all. 1 May 29, 1973 [54] APPARATUSFOR CUTTING OF FIBER [56] References Cited STRANDS UNITED STATES PATENTS[75] Inventors: ywg gg z E R::; g 2,851,103 9/1958 Anthony et a]...s3/913 x 1 745,965 12/1903 Lyon t ..83/355 [73] Assignee: Gebr. Bohler& Co. Aktien- 2,244,099 3/1941 Chase ----l46/ 121 R gesellschaft,Dusseldorf Germany 2,233,727 3/1941 Ball .241/19] X [22] Filed: 1970Primary ExaminerJ. M. Meister [21 Appl. No.: 18,274 Attorney-Holman &Stern [30] Foreign Application Priority Data [57] ABSTRACT An apparatusfor chopping strands of fibers in which 31 5 2 there is provided arotatable clamping head defined by y two disc-shaped members, means forforcing the mem- [52] U S 83/675 83/355 83/595 bers against each otherand chopping knives clamped n 83/698 83/913 between the disc members andprotruding therefrom, 51 int. c1. ..B2 6d 1/28 each knife being definedby a straight metal body [58] Field of Search ..83/355 356 591-594Substantially triangular cmss'section having first 83/675 698400, 913;71 tion clamped between the disc-shaped members and a 146/1 17423 secondportion protruding beyond the disc-shaped members, with the protrudingportion having a knife edge.

1 Claim, 8 Drawing Figures PATENTEM I 3,735,661

SHEEI 1 [IF 3 1 APPARATUS FOR CUTTING OF FIBER STRANDS BACKGROUND OF THEINVENTION This invention relates to apparatus for chopping strands offibers, such as cellulose fibers or man-made fibers, which apparatuscomprises a rotating cutter head in which the chopping knives aredetachably mounted.

The known forged chopping knives for making staple fibers consist of aknife blade having, in cross-section, a shape which approximates a veryacute-angled triangle, and a shank, which, in most cases, has thecrosssectional shape of a narrow rectangle. The two parts include anobtuse angle so that the shank is clamped in the head to extend in aradial direction whereas the blade lags by the obtuse angle during therotation of the cutter head. Such knives are made by forging, heattreating and grinding operations, which involve considerable labor andother costs. After a certain time of use, the knives are removed,re-ground and re-installed for further use.

SUMMARY OF THE INVENTION It is an object of the invention to provide,for the chopping of a strand into staple fibers an apparatus whichcomprises knives that can be made at lower cost and can be clamped andreplaced more easily. This is accomplished in that the blade and shankof the present chopping knives extend along. a straight line and have,in cross-section, an approximately constant shape, which is preferablysubstantially triangular.

A process of making such knives is characterized according to theinvention, in that steel is rolled to form a rod which has, incross-section, the shape of an acuteangled triangle, and sections havingthe overall length of a knife are severed from the rod. These sectionsare hardened, e.g., in a salt bath, and the narrow edge is sharpened bygrinding in the length which is required for the knife edge protrudingfrom the clamping head. The knives are so clamped in the clamping headthat the knife edge includes an obtuse angle with the radius so as tolag the rotating head. The openings which are formed in the clampinghead and serve for the fixation of the knives may conform to thetriangular crosssection. When knives having a shank of rectangularcross-sectional shape are sometimes used in the cutter head and theopenings are rectangular in cross-section to conform to the shank, ashim consisting of plastic material or another resilient material andhaving in cross-section the shape of an acute-angled triangle may beadhered to the shank.

To eliminate the need for the time-consuming fixation and removal andfor re-grinding, which can be performed only on special machines,another apparatus has been developed, which comprises discardableblades. The same are clamped throughout their length in holders andtheir portions provided with knife edges are similar in configuration tothe above-mentioned chopping knives. Such apparatus has the disadvantagethat fibers tend to be caught by the blade holders and require ashut-down of the apparatus.

For this reason, it is another object of the invention to avoid also thedisadvantages of these discardable blades which are clamped throughouttheir length. This is accomplished, according to the invention, in thatthe knife blades are clamped in the holders only in a length which isshort compared to the overall length of the blades. The length of theseblades, which freely protrude from the clamping head, is smallerapproximately by one-half than the length of the knives having a shankwhich is clamped. This fact accounts for a considerable saving of theexpensive material.

To enable such an arrangement, the clamping head is provided withholders which considerably protrude from the body of the clamping headin the directions of the axes of the knives. In a preferred embodimentof such apparatus, each knife blade is provided with one or two knifeedges extending throughout the length of the blade or only along theportion which protrudes from the clamping means. Blades having twocutting edges can be turned around and used twice.

It has proved desirable to use discardable blades in which the ratio ofthe clamped length to the overall length is smaller than 0.3. It is alsodesirable if the ratio of the thickness of the discardable blade to itsoverall length is 0.01-0.03. These discardable blades are made, inaccordance with the invention, from prerolled strip in which the knifeedges are formed on one or both edges of the blade by cold rolling andare subsequently hardened, e.g., by induction heating. This process ofmanufacturing discardable blades results in additional significantadvantages and savings in cost compared to the known knives which areforged and then ground and heat-treated, as well as to the knives havinga constant shape, e.g., a triangular shape, in crosssection. The use ofthese discardable blades eliminates the need for a removal andreplacement of knives and for a re-grinding so that the special machinesrequired for this purpose are not needed and skilled labor for this workneed not be employed.

Further details of the invention are apparent from the followingdescription of embodiments shown diagrammatically and by way of examplein the accompanying drawings, in which BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is an elevation showing a cutter head and a plurality of knivesaccording to one embodiment of the invention,

FIG. 2 is a longitudinal sectional view of the arrangement of FIG. 1,

FIG. 3 a transverse sectional view taken on line 3- -3 of FIG. 1 througha knife and the cutter head,

FIG. 4 is an elevation showing another embodiment of a knife according'to the invention,

FIG. 5 is a top plan view showing the knife of FIG.

FIG. 6 is an elevation showing another apparatus according to theinvention,

FIG. 7 is a longitudinal sectional view showing the apparatus of FIG. 6and FIG. 8 is a transverse sectional view taken on line 8-8 of FIG. 6through the cutter head.

The structures shown in the drawings may be described as follows.

DETAILED DESCRIPTION OF THE DRAWINGS evenly angularly spaced by an angle0). In its portion protruding from the cutter head, or throughout itslength, each knife is formed with a cutting edge 11. The knives 10 aremade from steel and are hardened throughout their cross-section or onlyadjacent to the cutting edges 11. The cutter head has side faces 7, 8which define the sides of the openings in which the knives are clamped.These side faces 7, 8 contact the clamped knives l and include an anglewhich is equal to the wedge angle 7 of the knives 10. The side faces 7,8 and the end faces 9 contacted by the edges of the knives 10 and theseedges themselves are inclined from the parting plane between the twodisc bodies 1, 2 of the clamping head and from the radii extendingthrough the axis of rotation X-Y. Desirable conditions will be obtainedif the angles 0: included by the cutting edges 11 and the radii are inthe range from 0-30. The two disc bodies 1 and 2 of the cutter head areheld together by screws 3. Adjacent to each opening formed in one discbody 2 and serving to receive a knife shank, the other body 1 mayaccommodate a plate 6, which is rectangular in cross-section andconsists of plastic material, such as polyvinylchloride. The plate 6 isdisposed in a groove and protrudes from the disc body 1. Each of theseplates 6 may be secured to the disc body 1, e.g., by means of twoflathead screws 4 and ensure a uniform contact pressure at the clampedsurfaces of the knives 10. Each knife 10 is provided with a fixing hole13, which in the knives shown in FIGS. 1 to 5, is spaced from back 12 ofthe knife by a distance b, which is much smaller than the distance afrom the hole 13 to that edge of the knife which is provided with thecutting edge 11. The fixing hole 13 is fitted over a pin screw providedin the disc 2.

The knife which is shown in FIGS. 4 and 5 comprises a part 100, whichconsists of steel and is triangular in cross-section and provided withthe cutting edge 11a, and a plate 14, which is also triangular incross-section and consists of plastic material, such aspolyvinylchloride. The plate 14 is secured, preferably adhered, to thatend portion of the part a where the latter is to be clamped so that theknife is rectangular in crosssection in that end portion and can beclamped in existing cutter heads which have rectangular openings ofconstant width.

FIGS. 6, 7 and 8 show an apparatus which embodies the invention and inwhich knives 30 consist of short and thin discardable blades, which havetwo cutting edges so that they can be used twice. The holders protrudefrom the edge of the disc-like halves or bodies 21, 22 of the bipartiteclamping head by a distance 0, which is equal to the length in which theknives are to be clamped, and in the direction in which the clampedknives extend. This direction is determined by the angle B. The portionin which the knife blades are clamped in the holders of the bipartite,rotatable cutter head has a relatively short length 0. The knives 30protrude from the cutter head. All holders are equally spaced from theaxis of rotation X-Y and are spaced apart by like angles 1. Each knifeblade 30 is provided with two parallel cutting edges 31, 32, whichextend throughout the length e of the blade and in crosssection have theshape of a rectangle and two triangles adjoining the ends of therectangle. The bodies of the knife blades 30 consisting of hardenablesteel are heattreated. Their knife edges 31, 32 are formed, e.g., bycold rolling and grinding and are hardened by high frequency inductionheating. The knife blades 30 could be hardened throughout and, in thiscase, would have a Rockwell hardness above 50. The cutter head is formedwith side faces 27 and 28, which contact the clamped knife blades. Thesefaces 27 and 28 and the knife blades themselves extend at an angle tothe parting plane of the cutter head. This angle is determined in viewof the ratio of the feeding speed of the strand to be chopped to theperipheral velocity of the blades. Those edges of the knife blades 30which are formed with the knife edge portions 31, 32 contact end facesof the openings and these end faces as well as the knife blade edgesformed with the cutting edges are inclined from the radii which extendthrough the axis of rotation X-Y. This inclination (5,8) may desirablybe within the range from 030. Helical compression springs 26 areprovided between the bodies 21 and 22 of the cutter head, which bodiesare held together by screws 23. A known permanent magnet system 34 isfixed in the body 22 adjacent to each holder and a protruding retainingpin 25 is fixed to the body 22 on that side of each magnet system 34which faces the axis of rotation X-Y. Each knife blade 30 has, formed inan end portion, a hole 33, which is fitted on one of the retaining pins25. Spacing flathead screws 24 are screwed into the body 21. Each of thescrews 24 is held against rotation by a spring lock washer and a hexagonnut and extends through a bore in the body 22. When the operativeleading cutting edges 31 of the knife blades 30 fixed in the cutter headhave become blunt after a prolonged use, the screws 23 are somewhatloosened to form a clearance between the body 21 and the knife blades30, which adhere to the permanent magnetic systems. The knife blades 30can now easily be turned around or replaced by new ones by hand. Thepermanent magnet systems 34 facilitate these operations.

The knife blades used in the apparatus according to the invention arenot re-ground, as a rule. Nevertheless the work using such apparatus ismuch less expensive than the use of the known apparatus provided withchopping knives which must be reground.

The invention comprises also apparatus in which the straight knives areclamped by other suitable means or in which the knives have differentcross-sectional shapes, which are constant throughout the length of theknives. For instance, cross-sectional shapes may be used which consistof two acute-angled triangles forming, e.g., a diamond, or which havedifferent cutting angles for cutting different materials and are similarto a rhomboid.

I claim:

1. In an apparatus for chopping strands of fibers, such as cellulosefibers and man-made fibers, a rotatable clamping head constituted by twodisc-shaped members, means forcing said members against each other andchopping knives clamped between the disc members and protrudingtherefrom, each knife including a straight level body of substantiallytriangular crosssection having a first portion adapted to be clampedbetween the disc-shaped members and a second protruding portion, saidsecond protruding portion having a knife edge, said second portion ofthe body being provided with a hole for receiving a screw for fixing thebody in the clamping head, and the distance between the side of thesecond portion of the body having the knife edge being greater than thedistance between the hole and the other edge of the protruding portionof the body.

i i i

1. In an apparatus for chopping strands of fibers, such as cellulosefibers and man-made fibers, a rotatable clamping head constituted by twodisc-shaped members, means forcing said members against each other andchopping knives clamped between the disc members and protrudingtherefrom, each knife including a straight level body of substantiallytriangular cross-section having a first portion adapted to be clampedbetween the discshaped members and a second protruding portion, saidsecond protruding portion having a knife edge, said second portion ofthe body being provided with a hole for receiving a screw for fixing thebody in the clamping head, and the distance between the side of thesecond portion of the body having the knife edge being greater than thedistance between the hole and the other edge of the protruding portionof the body.